1. Field of the Invention
This invention generally relates to a sprocket for a bicycle transmission. More specifically, the present invention relates to a rear sprocket for a bicycle transmission having a large number of rear gears or sprockets.
2. Background Information
Bicycling is becoming an increasingly more popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving the various components of the bicycle. One component that has been extensively redesigned is the bicycle transmission.
Over the past several years, bicycle riders have desired an increased number of speeds or gear ratios available in bicycle transmissions. Thus, over the past several years, the bicycle industry has increased the number of sprockets installed on the rear-wheel sprocket assembly of bicycles in order to provide additional different gear ratios. Specifically, road bicycles have seen the number of rear sprockets increase from five (5) to nine (9) to provide additional different gear ratios for the bicycle transmission. Mountain bicycles have also seen the number of rear sprockets increase -similarly. Even more recently, in more recent years, the number of rear sprockets has increased from nine (9) to ten (10) rear sprockets on some bicycles (i.e. road bicycles in particular).
While these ten (10) speed rear sprocket assemblies work well, they suffer from some deficiencies. In particular, ten (10) speed rear sprocket assemblies are typically wider in the axial direction than the previous nine (9) speed rear sprocket assemblies. Accordingly, it can be difficult or even impossible to mount the ten (10) speed rear sprocket assemblies on some rear freewheel assemblies that were originally designed for nine (9) rear sprockets. Additionally, even if the ten (10) speed rear sprocket assemblies can be mounted on rear freewheel assemblies that were originally designed for nine (9) rear sprockets, shifting performance can be adversely affected.
More specifically, in the current the ten (10) speed rear sprocket assemblies, the sprockets and the spacers have typically been constructed to be slightly narrower than the previous nine (9) rear sprockets and spacers, and a narrower chain has been utilized in order to achieve the desired shifting performance with the increased number of rear sprockets. However, even when such modifications are made, the ten (10) speed rear sprocket assembly (cassette) is still typically about 1.0 millimeter wider than a nine (9) speed rear sprocket assembly (cassette). Accordingly, if a ten (10) speed rear sprocket assembly (cassette) is mounted in the current manner, the top sprocket (smallest, outermost sprocket) is located laterally outwardly by about 1.0 millimeter more than the top sprocket of a nine (9) speed sprocket assembly (cassette) mounted on the typical freewheel. In some cases, this arrangement may result in the chain touching the bicycle frame when the chain is located on the rear top sprocket (e.g. if the chain is also located on the front top sprocket or largest outermost front chain ring and/or in certain riding conditions).
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved rear sprocket for a rear sprocket assembly. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.